1. Field of the Invention
The present invention relates to an optically coupled semiconductor device which is applied to a measuring instrument such as a tester and a method for manufacturing the device.
2. Description of the Related Art
Recently, a non-contact relays such as an optically coupled semiconductor device has been used in an increasing number of cases in order to improve reliabilities. A tester uses thousands of optically coupled semiconductor devices therein in some cases, so that miniaturization of the optically coupled semiconductor devices is desired greatly in order to miniaturize the tester. Based on such a market trend, a variety of optically coupled semiconductor devices have been developed.
One of such optically coupled semiconductor devices is disclosed in, for example, Jpn. Pat. Appln. Laid-Open No. 11-163705. This optically coupled semiconductor device has, as shown in FIG. 10, a wiring substrate 23, in which a recess 24 and a wiring pattern (not shown) are formed. A light-emitting element 25 is die-bonded to a bottom of the recess 24 in the wiring substrate 23 and wire-bonded by a gold wire 26.
Furthermore, on the wiring substrate 23, there is provided a photo-receptor element 29 in such a manner as to cover an upper-side opening of the recess 24 and to be opposite to the light-emitting element 25. The photo-receptor element 29 is flip-chip bonded to the wiring substrate 23 via a bump 34.
On the same surface of the wiring substrate 23 as that on which the photo-receptor element 29 is mounted, a switching element 27 is flip-chip bonded via a bump 28. The photo-receptor element 29 and the switching element 27 are electrically connected with each other through a wiring pattern, not shown, on the substrate 23.
A space between the light-emitting element 25 and the photo-receptor element 29 is filled with a translucent silicone resin 30, while the photo-receptor element 29 and the switching element 27 on the wiring substrate 23 are both sealed with a light-blocking resin 31.
In this optically coupled semiconductor device, by mounting the photo-receptor element 29 and the switching element 27 by flip-chip bonding, it is possible to eliminate a necessity of forming a pad for wire bonding, thereby miniaturizing the optically coupled semiconductor device.
It is to be noted that this switching element 27 in this case needs to be constituted of a lateral double diffused MOSFET in which a gate, a source, and a drain are in the same plane of a chip. In a case where a switching element is used in which a drain electrode is formed on a back face of the chip, it is to be mounted by wire bonding as shown in FIG. 11.
However, there have been the following problems conventionally.
First, when die-bonding the light-emitting element 25 into the recess 24 in the wiring substrate 23 and wire-bonding it, it is necessary to set a size of the recess 24 large so that a capillary of a wire bonder may not interfere with the wiring substrate 23. Therefore, the light-emitting element 29 covering the recess 24 becomes large more than necessary.
It is to be noted that although the size of the recess 24 might be reduced by using a capillary having an extremely thin tip, such a capillary is deteriorated in durability and ultrasonic vibration characteristic, thus deteriorating productivity greatly.
Further, since the wiring substrate 23 needs to have an additional substrate area for mounting the switching element 27 besides an area for forming the recess 24, it has been difficult to miniaturize the optically coupled semiconductor device further.